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Discussion Starter #1
Hello,

I was wondering if anyone has seen this happen. I was pulling a 7500 lbs loaded trailer up a long hill in 3rd gear and all of a sudden the indicator around the 3rd gear disappeared. The tranny gauge was almost near the top of the normal range and the truck was going 45 mph on 3rd. I tried pushing the gear button to take it back to D or 4th to no avail. As soon as I reached the top of the hill and the tranny cooled off a bit, the indicator mark came back.

Has anyone seen this before?

Mike
 

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Yes, I've had it happen on a couple of occasions while towing up grades in the summer time. I have a non BT so I don't have a trans temp gauge; I always assumed it meant the transmission was getting hot.

I take it as a form of admonishment and try to downshift into 2nd gear sooner next time. :bangit:
 

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Ah har... we're not crazy after all. I've had this happen when I've not been paying attention to how hard the tranny is working. I tow a lot through the mountains, since I live there. My indicator will go out and the trans resorts to its 'safe mode' programming. Shifts are rock-hard because they're not being modulated by unlocking the torque converter.

More in this thread.

Yup, been there, seen that a lot. After the transmission cools off a bit, you have command of it again.

Hope that helps.
 

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Discussion Starter #6
That really stinks and it goes contrary to what Nissan calls 'Normal operating range'.
When this happened to me, the tranny temp was slightly below the second mark from the top, not in the 'do not drive zone'.
So how can this be normal if the computer needs to take over the shifting?

Mike
 

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Discussion Starter #7
Is the concluding answer to this problem, 'you have a tranny issue' or is it 'this is the computer taking over'?
I am not sure that I can conclude either one.

Mike
 

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No, the transmission ECU programming is protecting the transmission. If you seriously overheat everything, the trans ECU will tell the engine ECU to kill power so you have to pull to the side of the road to cool it all off.

I had some conversations with a Nissan powertrain designer several years ago, and the sampling for the temperature indicator on the dash is taken (was at that time) where the highest readings will be generated - at the fluid exit of the trans, en route to the cooler. So the actual transmission fluid temperature in the transmission itself is much cooler. According to him, the ECU has access to readings from other sensors in the transmission, and when it takes over from you, it's found too much of an overall rise in temperature, so it grabs control to make sure that the transmission stays within its safe operating range.

It's operating normally.

Hope that helps explain it a bit.
 

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Discussion Starter #9
Thanks for the quick response. I still don't understand why Nissan says that it is operating normally yet the tranny ECU needs to take over. No big deal, as long as I am not frying anything I welcome the ECU help.
You seem to know quite a bit about the tranny and I was wondering if you could answer a question.

I am planning to get a BD GT and a larger PML trans pan. The pan can be ordered w/ a sensor hole or w/o it.
Does the BD GT read the temp from the ECU plug or do I need to wire a special sensor to the PML trans pan to get an accurate read?
In other words, if I have a BD GT do I need to order a pan w/ the sensor hole in it?

Thanks again,

Mike
 

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I still don't understand why Nissan says that it is operating normally yet the tranny ECU needs to take over. No big deal, as long as I am not frying anything I welcome the ECU help.
Nissan only allows so much 'manual' control of the transmission. They programmed it this way to prevent somebody from wrecking it due to neglect or abuse. So as I understand, it's supposed to grab control back in plenty of time before anything "bad" happens.

The transmission guy in our shop (million years ago) used to have a saying for people who abused their automatics: "Hey, it's not a stickshift, ya know??"

Does the BD GT read the temp from the ECU plug or do I need to wire a special sensor to the PML trans pan to get an accurate read?
In other words, if I have a BD GT do I need to order a pan w/ the sensor hole in it?
Mike
Mike, the only people who can give you the straight answer are the BD people. From what I've seen on the forum here they seem to be really responsive. I'd go to their site and find the 'Contact Us' link and shoot them a quick email.

Anything I'd have is a guess; I try to give honest advice and answers (for what it's worth) and wouldn't want to lead you astray.
 
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